Fermentation Temps

[mgortel]

Mgortel- why would you set the keezer at 55F only to wrap a heater around the carboy to get it to 67F? Maybe I missed something but that doesn't make any sense to me. Why not just use one thermostat set at 67F?

That is what I read that others do.....and I believe the reason, which does make sense to me, is that if you set the freezer to 67F......during peak fermentation the actual beer will be 5-10 degrees higher than ambient.

SO.....the 55F ambient temp takes away the heat of fermentation....but to make sure it doesnt lower the beer temperature too much the heater cycling on and off keeps the beer at fermentation temp of 68F.....

Once the peak fermentation is over you could just turn off heater wrap and set freezer to 68F for example

ANyone else that does this...can you chime in....to confirm

 

[bobbrews]

I think that if you're using a confined temperature regulated chest cooler, you should set it to the desired fermentation temperature. The cooler should keep the wort stable at that temp. give or take a degree.

The rule of thumb that fermentation temp. will always a little higher ambient temp. seems to me, to only be applicable when you are NOT using a temp. regulated chest cooler, i.e. just letting the carboy sit on the floor in your home with fluctuating temps. and air flow.

 

[SpeedYellow]

No, I don't think it's at all typical to use two thermostats running a keezer and a heater both fighting against each other at the same time. Yes it could work, but would waste a lot of energy in addition to requiring you buy another tstat and heater. It's just nonsensical. And it doesn't save any effort since you still have to play with the settings during the course of fermentation.

There are really only two sensible ways to do this: (1) attach your tstat probe to, or inside, your fermenter such that the tstat is measuring the beer temp and cooling the air accordingly, or (2) use the tstat to measure and control the ambient air. Method #1 can result in greater temp swings in your beer, but is more convenient since it is set-it-and-forget-it. Method #2 can give more stable beer temps but requires you to tweak settings during fermentation due to the varying heat generation within the beer.

 

[SpeedYellow]

...
The rule of thumb that fermentation temp. will always a little higher ambient temp. seems to me, to only be applicable when you are NOT using a temp. regulated chest cooler, i.e. just letting the carboy sit on the floor in your home with fluctuating temps. and air flow.

My experience proves otherwise. As long as the beer is creating heat (during peak fermentation) it's essentially impossible for the beer to be at the same temp as ambient. How you control the ambient (I.e. on the floor versus in a fridge) has nothing to do with that. A fan or water bath may decrease the differential, but that has nothing to do with being in a fridge or not.

 

[mgortel]

My experience proves otherwise. As long as the beer is creating heat (during peak fermentation) it's essentially impossible for the beer to be at the same temp as ambient. How you control the ambient (I.e. on the floor versus in a fridge) has nothing to do with that. A fan or water bath may decrease the differential, but that has nothing to do with being in a fridge or not.

I agree 100%.....if the yeast/beer is generating heat in the bucket the heat has to transfer somewhere.....heat flows from hot to cold....sooooo....the temperature of the wort has to be higher than the ambient by an amount adequate to transfer the heat at a rate equal to the generation by the yeast doing their thing.

If the surroundings are large...i.e. a basement.......the ambient temperature does not change from the heat transferred from the bucket to the basement....so the beer temp rises until the temp difference is enough between beer and basement to transfer heat generation.

BUT....if the surroundings are small, like a freezer or small insulated enclosure....the heat builds up and increases the heat in the AMBIENT air around the bucket (i.e. in the freezer, chamber, fridge, whatever)....so the beer temp has to go even higher.....UNLESS you keep temperature in freezer, fridge, constant by having it cycle on and off to remove heat....

So the beer has to be at a higher temperature than the ambient....as everyone has witnessed I am sure.....at the begginning of yeast activity.....first several days.

 

[bobbrews]

BUT....if the surroundings are small, like a freezer or small insulated enclosure....the heat builds up and increases the heat in the AMBIENT air around the bucket (i.e. in the freezer, chamber, fridge, whatever)....so the beer temp has to go even higher

Heat does not build up because the temperature control of these types of units are highly regulated. If the sensor notices a rise, it quickly turns on the cooling fan to adjust the temperature back to the stated level.

Heat is created by fermentation, but it's miniscule at about 3-5 degrees. Any changes in the chest cooler temp. via the heat given off by fermentation will be subsequently and very quickly adjusted again by the temp. regulated chest cooler thus balancing everything out at the temp. you originally set. If you're simply fermenting in a closet on a wooden floor, temp. fluctuation is much more erractic and not easily controlled.

Fermenting wort inside a glass or plastic carboy barrier is not exactly a temperature impenetrable surface whereupon the restrictive size of a chest cooler is completely incapable of regulating, if set at the desired fermentation temperature. There's absolutely no need to set it at a lower temperature unless your unit does a piss poor job at temp. regulation.

 

[mgortel]

Exactly....that is why the need to have the chest freezer controlled to a cooler temp than the fermentation temp......

But.....keeping the beer from getting to cold is the trick........thats where the heater and second controller comes in....based on the beer temperature...i.e. temp probe in beer

Otherwise its a guessing game. I think we are on the same page here....

I know I saw a post where some others do it this way and swear by it....

 

[bobbrews]

Read the last paragraph again.

 

[mgortel]

If you keep ambient temperature at your desired fermentation temperature.....your fermentation temperature WILL BE HIGHER than the ambient temperature....period. It has to be....otherwise it violates the First Law of Thermodynamics.....period.

In my experience it can be as much as 5-10 degrees F....depends on the beer. Now once active fermentation ends then of course beer will settle at the ambient temperature.

 

[bobbrews]

Agree to disagree. I'm not saying that fermentation does not occur without an added heat. But if you have a unit that is fairly precise at regulating temperatures, then the miniscule amount of heat emitted by active fermentation per hour will be re-adjusted by the cooling fan in a matter of seconds, thus negating the effects of any heat driven off via fermentation and balancing the temperature back to what you originally set it at. This is not the case when the fermentor is sitting at ambient room temps. because your home's atmosphere is not nearly as precise at controlling temperature as a chest cooler. That is sort of the whole reason people get chest coolers!

 

[mgortel]

LMAO....we should just say the hell with the discussion and get together for some homebrews! Sound like (2) politicians....haha

 

[bobbrews]

Do you think that somehow, if you place a carboy inside a regulated 65 F chest cooler, that active fermentation will magically raise the wort temperature to 70-72 F so quickly that the chest cooler has a difficult time maintaining the original 65 F temperature originally set forth? Because it doesn't work that way my friend. The chest cooler will have no problem maintaining temp. increases in a matter of seconds... Which is much faster that active fermentation could ever raise the temperature by several degrees.

 

[SpeedYellow]

Agree to disagree. I'm not saying that fermentation does not occur without an added heat. But if you have a unit that is fairly precise at regulating temperatures, then the miniscule amount of heat emitted by active fermentation per hour will be re-adjusted by the cooling fan in a matter of seconds, thus negating the effects of any heat driven off via fermentation and balancing the temperature back to what you originally set it at. This is not the case when the fermentor is sitting at ambient room temps. because your home's atmosphere is not nearly as precise at controlling temperature as a chest cooler. That is sort of the whole reason people get chest coolers!

This isn't a matter of opinion; what you're arguing is observably false. It makes no difference if you're using a fridge or just setting the fermenter in a basement corner; the beer will always be 3-10 degrees warmer than the ambient air during peak fermentation. Clearly you've never tested your pet theory.

 

[mgortel]

Absolutely.....have you not experienced this yourself.....

The chest freezer air temperature will absolutely be at 65F.....BUT THE BEER TEMPERATURE......WILL BE HIGHER by as much as 4,5....even 7 or 8 degrees during active fermentation. Remember the fermentation temperature you need to be concerned with is that of the BEER itself...not the chamber in which it sets. Just because the ambient (freezer, fridge, basem,ent) temperature is at a certain level it does not mean the beer temp is at thet level.

DO you have fermometers on your carboys or ale pails....??? Have you never noticed that during active fermentation your beer temperature is 4-5 degrees higher than the ambient temperature...maybe more??

Here is a good example of a post by someone experiencing this exact issue https://www.homebrewtalk.com/f163/basement-fermentation-368930/

At a minimum you have to set your ambient temp several degrees lower than you want your beer to ferment at....otherwise your beer will be actively fermenting at a higherr temp than you desire...

 

[bobbrews]

I have been brewing for several years with and without the assistance of a chest cooler for fermentation. And I have never had 3-10 F wort swing increase when the chest cooler was set to a lower temp. during active fermentation.

I have experienced that increase with fermentation when not using a chest cooler though. FYI - Using both a fermometer and a wired digital thermometer, where the probe sits in the wort.

 

[SpeedYellow]

Do you think that somehow, if you place a carboy inside a regulated 65 F chest cooler, that active fermentation will magically raise the wort temperature to 70-72 F so quickly that the chest cooler has a difficult time maintaining the original 65 F temperature originally set forth? Because it doesn't work that way my friend. The chest cooler will have no problem maintaining temp. increases in a matter of seconds... Which is much faster that active fermentation could ever raise the temperature by several degrees.

Simply 100% patently false. Indeed the chest cooler will hover around 65F and the beer will be around 70F for a couple days. You're arguing against what everyone knows to be fact based on our own observations.

 

[bobbrews]

Read above. Those are my observations.

In that small, temp. controlled space, it's odd that you believe the 65 F air conditioned unit with a powerful cooling fan (which activates every couple minutes) is incapable of nonstop temp. regulation. Regulation which can penetrate wort through a carboy... which in your opinion must be always be several degrees higher during active fermentation, thus rendering the chest cooler completely useless if not also set several degrees lower than desired fermentation temperature.

And who's everyone? You and mgortel? It makes me think whether or not YOU ever tested your theory.

 

[mgortel]

it's odd that you believe the 65 F air conditioned unit with a powerful cooling fan is incapable of nonstop temp. regulation, or penetrating the wort through a carboy, which in your opinion must be several degrees higher during active fermentation, rendering the chest cooler useless if not also set several degrees lower than desired fermentation temperature. And who's everyone? It makes me think if YOU ever tested your theory.

Would EVERYONE please chime in to help bobrews understand this.

Bob...I think you would significantly increase the quality of your beer if you would listen to what we are saying....and pay very close attention to the temps on your next batch of beer. Monitor the ambient temperature and the ACTUAL beer temperature for the fisrt 36-48 hours.....just check both every 8-12 hours and write it down. Stick a adhesive backed fermometer on your carboy or ale pail.

Guarantee you will see what we are saying. Just trying to help.....

 

[SpeedYellow]

It's not that I believe the fridge's air temp is cooler than the beer, I know it's the case. I graph the temps on all my fermentations, and it's always the same story. Here's an example from my latest batch. The ambient temp is a glass of water sitting right next to the carboy. Temps are taken with the same lab thermometer. You can see that when fermentation finishes (CO2 output, shown by "o" markers), the ambient and beer temp converge. Same every time.

 

[meadmazer]

As a refrigeration tech, here are my thoughts, FWIW. Heat flows only one way, from heat to "less heat". The fermenting beer is creating heat, being removed by various means. Water bath evaporation, freezer evap coil, etc.
As the "beer container" creates heat, the temp increases in the surrounding "secondary" refrigerant, air or water or whatever is being cooled that is in turn cooling the beer. For this to happen there must absolutely be a temperature difference, the beer must be warmer than the cooling medium. Laws of thermodynamics etc as stated above. Can a good setup get the air temp back to setpoint in a few seconds as bobbrew states? Sure, absolutely. Does this immediately get the beer to the setpoint? No, it doesnt work that way. In fact, now the temp diff is even more, until the beer cools down slightly as the air, in turn, warms up. To keep the beer at an absolute setpoint the amount of heat being removed by the cooling system needs to match EXACTLY the amount of heat being generated by the fermenting beer. Any system that cycles on and off, by definition, is not doing that, or it wouldnt be cycling. It would need to be infinitely variable, full time, like the fermenting beer. Even then, there would still be a temp difference between the beer and the medium, or there wouldnt be any heat flow ie cooling taking place. You CANNOT have EXACT temps between beer and secondary coolant, as long as heat is being produced by fermentation, or heat cant be removed. Not possible, cant happen. The more heat being produced by the beer, the more heat needs to be removed. If your system is efficient enough, and lag time on your temp probes is high enough, you may not see the constant temp changes between the beer and air, but they indeed are there. You may just see an "average" temp, but even then, the coolant has to be a bit lower than the beer. Physics. Put a ambient temp probe in a cup of water, glycol, whatever and set it in the chamber with the beer. This will slow down the temp swings and give a more avg reading. Seal it so that there is no evaporative cooling going on to skew things. The beer temp probe is in your fermenting beer. If the probes are EXACTLY calibrated to each other you should see a average Td between the beer and water. Will it always be between such and such degrees 3 to 8 or whatever? No, depends on the efficiency of the system, heat being produced by the beer, air flow in the chamber, etc. Might only be fractions of a degree. But it must be there, can get around physics. You will most likely also have different temps at different locations in the chamber, just like in the fermenting beer; find the right locations and you may think that, according to you temps probes, you are proving physics wrong. Remember you are looking for average temps.

 

[daksin]

Regulation which can penetrate wort through a carboy... which in your opinion must be always be several degrees higher during active fermentation, thus rendering the chest cooler completely useless if not also set several degrees lower than desired fermentation temperature.

I think this is the part that we take issue with. 5 gallons of OG 1.040 beer weighs near-as-makes-no-difference 20kg, which is a fair amount. Water (beer) is a great insulator, as is the plastic or glass you've used to contain it.

On top of that the beer is generating its own heat (this is important- it's not just warmer than the environment, it's actually warming itself) and not moving much (a little, but not enough to increase convection via the insulating container). Add to that the fact that the hysteresis of the thermostat will result in chamber temps regularly warmer than the set point, and you almost certainly will have a warmer wort temp than the airspace. Convection of cool air at 65F around an insulated vessel of significant mass won't give you enough of a deltaT to rapidly cool the wort/remove the heat being generated.

That's IF the probe is just hanging out on the other side of the chamber, not touching the fermentor. If you get the probe in the wort or right up against the vessel and insulated from the air in some way, then you're right- the chamber is going to maintain a fairly (!) constant wort temp. Both ways will work- many people keep the ambient temp just a few degrees below their desired ferment temp and that works great for them, they just need to adjust it as fermentation slows.

 

[Phunhog]

You are guys are doing all wrong!! I have found the best solution is too ferment in a water bath and use a stainless sanke keg as your carboy. You can control the temperature of the water bath via an aquarium heater(heat) and a pump and immersion chiller (cool). I think the biggest problem you guys are facing is that plastic and especially glass are "insulators"....meaning that the wort/beer is somewhat insulated from external temperatures. Stainless, while not perfect, is a much better conductor of heat than glass or plastic. If my keg is sitting in a temperature controlled water bath there is no way the wort/beer temperture is going to exceed that temperature.

 

[bobbrews]

Bob...I think you would significantly increase the quality of your beer if you would listen to what we are saying

Lol, you have no idea. But I'm up to the challenge, especially vs. you.

So when are we trading? We should get some third party perspective as well.

Monitor the ambient temperature and the ACTUAL beer temperature for the fisrt 36-48 hours.....just check both every 8-12 hours and write it down. Stick a adhesive backed fermometer on your carboy or ale pail.

I do all this plus more. You are not reading what I am writing.

 

[bobbrews]

As a refrigeration tech, here are my thoughts, FWIW. Heat flows only one way, from heat to "less heat". The fermenting beer is creating heat, being removed by various means. Water bath evaporation, freezer evap coil, etc.
As the "beer container" creates heat, the temp increases in the surrounding "secondary" refrigerant, air or water or whatever is being cooled that is in turn cooling the beer. For this to happen there must absolutely be a temperature difference, the beer must be warmer than the cooling medium. Laws of thermodynamics etc as stated above. Can a good setup get the air temp back to setpoint in a few seconds as bobbrew states? Sure, absolutely.

Agreed. And I said nothing to the contrary. I'm glad someone understands that colder air is required to maintain temperature from rises in heat. So if you're aim is 65 F, and over the course of 1 hour, the temp. raises by 2 degrees, very cold air has already kicked in beforehand to lower the air temperature so that it is stabilizes once again at 65 F. It may even linger at 63/64 for a few minutes. I'm not sure if everyone knew this, but I thought it was fairly simple to understand and I'm not a refrigeration tech. Now, this doesn't always mean that air temp and wort temp will be equal. I am not arguing that. But if your unit is working as it should, then you shouldn't see the large swings we see under normal fermentation circumstances without the assistance of a regulated cooler.

Does this immediately get the beer to the setpoint? No, it doesnt work that way.

Agreed. But active fermentation isn't a lightswitch either that instantly boosts wort temperature 5-10 degrees higher than the air when fermenting, especially in a highly controlled cooling unit. The rises are more miniscule and gradual than that, so this is a null issue. There is certainly temp. fluctuation by the fermenting wort, but it is being controlled continuously by the cooling unit enough to prevent the active ferm. temp. from skyrocketing in a steady spiral like we see in instances where brewers do not use regulated coolers. At most, your increases in ambient air temperature within the chest cooler should only be a few degrees, which is continuously being lowered... not 5-10 degrees. With that kind of constant control, it's also not feasible that the active fermentation temp. will ever increase by 5-10 degrees. I have personally never experienced this anyway.

 

[SpeedYellow]

You are guys are doing all wrong!! I have found the best solution is too ferment in a water bath and use a stainless sanke keg as your carboy. You can control the temperature of the water bath via an aquarium heater(heat) and a pump and immersion chiller (cool)....

LOL. A somewhat simpler solution is to simply turn that little t'stat knob just 3-5 degrees lower. Thanks anyway.

 

[meadmazer]

Yes I see I went abit askew of original thread question, my bad.
To comment on the original question directly, fermentation temp will be much more accurate if the temp probe is in the beer and showing the temp of the fermenting beer, as opposed to the probe in air, where it would be showing the ambient temp. That way the controller is changing air temp, as needed, to control beer temp. I also agree that a cooler/heater regulating off the temp probe in the beer will be the most consistent/accurate. You could even put more than one in, at different depths, to get an even better average. Then we can always debate "what depth should I put the probe in the FV for best results"
I would look at using a fridge/freezer to ferment and just using the built in temp device as improvement number 1 to controlled ferm temps, with a dedicated controller as improvement number 2, over doing what most of us probly do, myself included, which is set the FV somewhere that is near the temp you want, and RDWHAHB.

 

[bja]

In that small, temp. controlled space, it's odd that you believe the 65 F air conditioned unit with a powerful cooling fan (which activates every couple minutes) is incapable of nonstop temp. regulation. Regulation which can penetrate wort through a carboy... which in your opinion must be always be several degrees higher during active fermentation, thus rendering the chest cooler completely useless if not also set several degrees lower than desired fermentation temperature.

You're completely wrong here. Cooling 5 gallon of liquid does not happen immediately.

 

[SpeedYellow]

.... fermentation temp will be much more accurate if the temp probe is in the beer as opposed to the ambient temp. ....

Not sure what you mean, since this statement doesn't actually make any sense. Say you have a t'stat with 1F differential. You can put the probe in the beer, and you'll always get swings of 1F in the actual beer temp. OTOH, you could leave the probe in the air, and you'll see less than 1F swings in the beer temp due to the thermal capacitance. But here, you're no longer measuring beer temp, but rather air temp, so you have to monitor beer temp then and set the t'stat lower than desired beer temp.

So the issue is not "accuracy" but rather how much temperature swings or hassle you're willing to accept.

 

[bobbrews]

You're completely wrong here. Cooling 5 gallon of liquid does not happen immediately.

Thankfully I never said that. But let's go back to what you and others are wrong on... A 5-10 F increase of 5 gallons of liquid in a temperature controlled cooler does not happen immediately.

 

[AnOldUR]

You are guys are doing all wrong!! I have found the best solution is too ferment in a water bath . . .

I've also moved to a water bath solution. Tested with thermowell and found that the bath is never a degree off from the wort temperature. Below is an extreme example of what I would get trying to control wort temperature by ambient air. One thermometer probe is hanging in the air, the other is taped to a glass carboy. During early fermentation I had to set the temperature control up to 10 degrees colder than I wanted the wort to be. As fermentation slowed, I’d gradually increase the temperature control over the first few days until it matched the wort temperature. PITA!